Buoyant polymer particles for delivery of therapeutic agents to the central nervous system

ABSTRACT

The invention provides compositions and methods for treating a subject who has suffered from a central nervous system disorder. More particularly, the invention provides sustained polymeric drug delivery systems for direct delivery of therapeutic agents into the central nervous system.

PRIORITY INFORMATION

[0001] This application claims priority to provisional patentapplication U.S. S No. 60/429,854, filed on Nov. 26, 2002, the entirecontents of which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

[0002] The invention provides compositions and methods for treating asubject who has suffered from a central nervous system disorder.

[0003] Historically, therapeutic intervention in neurological disordershas been limited by (1) a lack of understanding of the complicatedphysiological events of the disorder; (2) a lack of reliable animalmodels which mimic the human disorder to test product candidates; and(3) lack of adequate concentrations of drug reaching the injured braintissue. It has been difficult to achieve effective therapeutic drugtreatment of neurological disorders, because there are numerous chemicaland physical barriers which must be overcome in order for such adelivery to be successful.

SUMMARY OF THE INVENTION

[0004] The invention provides polymer compositions useful for deliveringtherapeutic agents for preventing or providing treatment forneurological disorders.

[0005] The invention features a biodegradable polymer compositioncontaining a therapeutic agent, a polymer and a buoyancy agent. Thecomposition is controllably buoyant in cerebrospinal fluid (CSF).

[0006] Buoyancy is conferred by the addition of at least one buoyancyagent. The degree of buoyancy is controlled by the amount of the agent.

[0007] In one embodiment, the polymer composition is neutrally buoyantin CSF. In another embodiment, the polymer composition is positivelybuoyant in CSF. In yet another embodiment, the polymer composition isnegatively buoyant in CSF. For example, the buoyancy agent is a gas. Forexample, the gas is air, i.e., the gas contains a mixture of oxygen andnitrogen. Alternatively, the buoyancy agent is a gas selected from thegroup consisting of nitrogen, argon, carbon dioxide, helium, and xenon.Alternatively, the buoyancy agent is a hydrofluorocarbon. An increase inpositive buoyancy is achieved by increasing the amount or composition ofthe gas or incorporating a lighter gas.

[0008] For the treatment of ischemic events such as stroke, theinvention provides a composition containing a therapeutic agent thatmitigates brain damage and/or that repairs brain damage as a result ofthe injury. The composition contains a biodegradable polymercomposition, with a therapeutic agent selected from the group consistingof inosine, citicholine, SOD and dextrorphan. For example, thecomposition includes a first polymeric particle comprising a firsttherapeutic agent and a second polymeric particle comprising a secondtherapeutic agent, wherein said first and said second polymericparticles comprise a buoyancy agent. The ratio of the first polymericparticle and the second polymeric particle is 50:50. Alternatively, theratio of the first polymeric particle and the second polymeric particleis 60:40 or 40:60. Mixtures of inosine-containing andciticholine-containing particle vary, e.g., 70:30, 80:20, 90:10, 30:70,20:80, or 10:90.

[0009] The mixtures are administered to subjects who have suffered astroke. The amount or ratio of therapeutic agent(s) in the mixturevaries depending on the length of time elapsed between the stroke eventand drug administration. For example, the longer the time elapsed fromischemic event, the greater the amount of inosine (relative tociticholine) is administered. If the combination drug treatment iscommenced relatively soon after an ischemic event, a greater amount ofciticholine is administered in the mixture. The drug mixture isadministered from one minute to one hour, to one day and up to one monthfollowing a stroke. The mixtures are delivered before, during, and afterdevelopment of an ischemic cascade following a traumatic event such asstroke.

[0010] Also included in the invention is a sustained biodegradablepolymer composition that is administered intrathecally to treat asubject who has been diagnosed as having a central nervous systemdisorder. The composition includes a plurality of polymer particles,each particle including a buoyancy agent and a therapeutic agent. Thebuoyancy agent allows the polymer composition to be targeted to or awayfrom the brain or spinal cord of the subject, therefore delivering thetherapeutic agent for an extended period of time to a targeted tissue totreat a subject having a central nervous system disorder.

[0011] The biodegradable polymer composition is suitable for intrathecaladministration to treat a subject having a central nervous systemdisorder and includes a plurality of polymeric particles containing atherapeutic agent and a buoyancy agent. The polymer compositioncircumvents the blood-brain barrier (BBB) and circulates within thecentral nervous system of the subject delivering the therapeutic agentto an injured region of the brain for an extended period of time. Theseimplantable devices are used to achieve continuous delivery oftherapeutic agents directly into the brain, spinal column, or relatedtissues for an extended time period. The polymer compositions areapplicable in the treatment of a variety of CNS disorders including, butnot limited to, cancer, Parkinson's disease, Alzheimer's dementia,Huntington's disease, epilepsy, Amyotrophic Lateral Sclerosis (ALS),Multiple Scleross (MS), antibiotic delivery, trauma, stroke, TraumaticBrain Injury (TBI), cerebral ischemia, depression, spinal cord injury,pain management and other types of neurological and psychiatricillnesses.

[0012] Polymers of the invention are naturally derived polymers, such asalbumin, alginate, cellulose derivatives, collagen, fibrin, gelatin, andpolysaccharides as well as synthetic polymers such as polyesters (PLA,PLGA), polyethylene glycol, poloxomers, polyanhydrides, polyorthoesters,and pluronics. The polymeric carriers of the present invention are usedas drug delivery vehicles. A wide variety of therapeutic agents areincluded in the compositions of the present invention and are describedherein.

[0013] For treating central nervous system lymphomas, cancertherapeutics such as members from the following classes are delivered,either alone or in conjunction with the above-mentioned therapeuticagents: vinca alkaloids and other plant products, cytostatic drugs,cytotoxic drugs, hormones (estrogens and anti-estrogens), alkylatingagents, immunomodulators (immunostimulators and immunosuppressives),hematological agents, non-steroidal products, radiopharmaceuticals,antibodies, antiandrogens, and epidermals.

[0014] The invention provides a method for distributing one or moretherapeutic agents within the central nervous system of a subject. Themethod includes delivering within the central nervous system a polymercomposition containing a plurality of polymeric particles, each particlecontaining one or more therapeutic agents and one or more buoyancyagents. The particles move up (positively buoyant), sink (negativebuoyant) or remain generally in the region of implantation depending onthe amount and/or nature of the buoyancy agents. The compositionbiodegrades and slowly releases the one or more therapeutic agents tothe subject having a central nervous system disorder.

[0015] Specific technical and scientific terms used herein have thefollowing meanings:

[0016] As used herein and in the claims, the singular forms “a”, “and”and “the” include plural referents unless the context clearly dictatesotherwise. For example, the term “a therapeutic agent” includes at leastone therapeutic agent.

[0017] As used herein, “central nervous system disorder” refers to anydisease state which is present in the brain, spinal column, and relatedtissues, such as the meninges.

[0018] As used herein, “cerebrospinal fluid”, “CSF” refers to acontinuous fluid system that fills the cerebral ventricles andsubarachnoid space (areas that surround the brain and spinal cord). Farmore than a shock absorber cushion of protection for the brain andspinal cord, the motion and flow of CSF is essential to the properfunctioning of the central nervous system. CSF bathes the neurons andglial cells of the brain and spinal cord; and as such it carriesnutrients as well as removes metabolic wastes and toxic substances fromthe central nervous system.

[0019] As used herein, “polymer” refers to molecules formed from thechemical union of two or more repeating units. For example, includedwithin the term “polymer” are dimers, trimers and oligomers. Forexample, the polymer is synthetic, naturally occurring or semisynthetic.In preferred form, the term “polymer” refers to molecules which comprise10 or more repeating units and are biodegradable.

[0020] As used herein, “sustained polymer delivery composition” refersto a polymer composition that provides continual delivery of atherapeutic agent in vivo over a period of time followingadministration. Preferably, delivery of a composition continues for atleast several days, a week or several weeks. Sustained delivery of thetherapeutic agent is demonstrated by, for example, the continuedtherapeutic effect of the agent over time (e.g., for ananti-inflammatory agent, sustained delivery of the agent is measured bycontinued reduction of fluid accumulation in the brain over time).Alternatively, sustained delivery of the therapeutic agent is monitoredby detecting the presence of the therapeutic agent in vivo over time.

[0021] As used herein, “pharmaceutically acceptable” and “biocompatible”refer to compounds, materials, compositions, and/or dosage forms whichare, within the scope of sound medical judgment, suitable for contactwith the tissues of human beings and animals without causing anyundesirable biological effects. Undesirable effects include excessivetoxicity, irritation, allergic response, or other complicationscommensurate with a reasonable benefit/risk ratio, and which do notinteract in a deleterious manner with any of the other components of thecompositions in which it is contained. Examples include, but are notlimited to, any and all solvents, dispersion media, coatings, polymers,antibacterial and antifungal agents, isotonic and absorption delayingagents, and the like that are physiologically compatible. Preferably,the composition is suitable for injection into the cerebrospinal fluid.Excipients include pharmaceutically acceptable stabilizers anddisintegrants.

[0022] As used herein, “subject” refers to animals. The term encompassesmammals, preferably humans.

[0023] As used herein, “therapeutic agent”, “therapeutic agents” aresubstances which alleviates a symptom of or prevents development of adisease or disorder. For example, the therapeutic agent(s) exert abeneficial biological effect in vitro and/or in vivo. The therapeuticagents may be neutral or positively or negatively charged.

[0024] As used herein, “neuroprotective agent” refers to drugs whichalleviate a symptom of or prevent damage to the brain or spinal cord.For example, such damage is the result of from ischemia, stroke,convulsions, or trauma. Some agents are administered before the event,while others are administered some time after an injury. They act by avariety of mechanisms, but often directly or indirectly minimize thedamage produced by endogenous excitatory amino acids.

[0025] As used herein, “intrathecal administration” means delivery intothe cerebrospinal fluid bathing the spinal cord and brain. Such deliveryis carried out using a variety of known techniques including lateralcerebroventricular injection through a burrhole or cisternal puncture(CP) or lumbar puncture (LP) or the like (described in Lazorthes et al.Advances in Drug Delivery Systems and Applications in Neurosurgery,143-192 and Omaya et al., Cancer Drug Delivery, 1: 169-179, the contentsof which are incorporated herein by reference). The term “lumbar region”means the region of the back lateral to the vertebral region and betweenthe rib cage and the pelvis. The term “cisterna magna” means the areawhere the skull ends and the spinal cord begins at the back of the head.The term “cerebral ventricle” means the cavities in the brain that arecontinuous with the central canal of the spinal cord. For example,administration of a therapeutic agent to any of the above mentionedsites is achieved by direct injection of the encapsulated therapeuticagent. For injection, the encapsulated therapeutic agents of theinvention is formulated in liquid solutions, preferably inphysiologically compatible buffers such as Hank's solution or Ringer'ssolution. In addition, the therapeutic agent is formulated in solid formand redissolved or suspended immediately prior to use. Lyophilized formsare also included. In a preferred embodiment, the injection is a single“one shot” LP administration.

[0026] The present polymers are in the form of a particle. The term“particle”, as used herein, refers to a three dimensional structure.Particles comprise, for example, a single molecule of a polymer, such asPLGA associated with one or more molecules of a therapeutic agent, or acomplex comprising a plurality of polymer molecules in association witha therapeutic agent. A wide variety of forms may be produced by theparticles of the present invention, including, but not limited to,rod-shaped devices, pellets, buttons, beads, slabs, capsules, spheres,pastes, threads of various size, films, fibers, sprays (see e.g.,Goodell et al., Am. J. Hosp. Pharm. 43:1454-1461, 1986; Langer et al.,“Controlled release of macromolecules from polymers”, in BiomedicalPolymers, Polymeric Materials and Pharmaceuticals for Biomedical Use,Goldberg, E. P., Nakagim, A. (eds.) Academic Press, pp. 113-137, 1980;Rhine et al., J. Pharm. Sci. 69:265-270, 1980; Brown et al., J. Pharm.Sci. 72:1181-1185, 1983; and Bawa et al., J. Controlled Release1:259-267, 1985). In a preferred embodiment of the invention,therapeutic agents are provided in non-capsular formulations such asspheres, including nanospheres and microspheres (ranging from nanometersto micrometers in size).

[0027] As used herein, “lymphoma” means cancer that arises from cells ofthe lymphatic system. Other cancer disease states may involve a varietyof cell types, including, for example, endothelial, epithelial andmyocardial cells. Included among the disease states are neoplasms,cancer, leukemia and restenosis injuries.

[0028] The therapeutic agents may be embedded within the wall of theparticle, encapsulated in the particle and/or attached to the particle,as desired. “Attached to” or variations thereof, as used herein inconnection with the location of the therapeutic agent, means that thetherapeutic agent is linked in some manner to the inside and/or theoutside wall of the particle, such as through a covalent or ionic bond,or other means of chemical or electrochemical linkage or interaction. Asused herein, “encapsulated in” or variations thereof as used inconnection with the location of the therapeutic agent denotes that thetherapeutic agent is located in the internal particle void. As usedherein, “embedded within” or variations thereof as used in connectionwith the location of the therapeutic agent, signifies the positioning ofthe therapeutic agent within the particle wall.

[0029] As used herein, “comprising a therapeutic agent” denotes all ofthe varying types of therapeutic positioning in connection with theparticle. Thus, the therapeutic agent ise positioned variably, such as,for example, entrapped within the internal void of the particle,situated between the buoyancy agent and the internal wall of theparticle, incorporated onto the external surface of the particle and/orenmeshed within the particle structure itself.

[0030] The compositions of the present invention are advantageously usedas delivery vehicles for therapeutic agents, particularly therapeuticagents that may have reduced or limited solubility in aqueous media. Aparticular advantage of the present invention is that controlled,sustained release of therapeutic agents is achieved with thecompositions described herein. As discussed in greater detail below, thetherapeutic agent is preferably substantially homogeneously dispersedthroughout the present particles. The term “substantially homogeneouslydispersed”, as used herein, means that the therapeutic agent may be atleast about 75% continuously dispersed throughout the particle, withabout 80% continuous dispersion being preferred. More preferably, thetherapeutic agent may be at least about 85% continuously dispersedthroughout the particle, with about 90% continuous dispersion being evenmore preferred. Still more preferably, the therapeutic agent may be atleast about 95% continuously dispersed throughout the particle, withabout 100% continuous dispersion (i.e., complete dispersion) beingespecially preferred.

[0031] As used herein, “controllably buoyant” means a polymercomposition that comprises at least one buoyancy agent. The compositionor amount of the buoyancy agent is adjusted to target it to or away fromthe brain or the spinal cord (the top or the bottom of the CNS).

[0032] Other features, objects, and advantages of the invention will beapparent from the description and from the claims. Unless otherwisedefined, all technical and scientific terms used herein have the samemeanings as commonly understood by one of ordinary skill in the art towhich the invention belongs. All patents and publications cited in thisspecification are incorporated by reference.

BRIEF DESCRIPTION OF THE DRAWINGS

[0033]FIG. 1 is a schematic showing delivery of pharmaceuticalencapsulated polymer (PEP) vehicle into the cerebrospinal fluid.

[0034]FIG. 2 is a general process flow diagram of the process of solventevaporation to produce PLGA pharmaceutical encapsulated polymer vehicle.

[0035]FIG. 3 is an image of PLGA/Inosine PCs.

[0036]FIG. 4 is a bar graph showing efficacy results afteradministration of various agents in a MCAo rat model of focal cerebralischemia by supracortical perfusion of the cortex.

[0037]FIG. 5 is a bar graph showing the dose-response curve forciticholine administered directly into the cerebrospinal fluid of ratsusing the rat middle cerebral artery occlusion (MCAo) model.

[0038]FIG. 6 is a bar graph showing the effects of the variousneuroprotectant agents on infarct volume in a rat model of focalischemia when delivered by the Supracortical perfusion method.

[0039]FIG. 7 is an image showing that Inosine stimulates nerve cells inundamaged parts of the brain to grow new connections into brain areasthat had lost their normal connections as a result of a stroke.

[0040]FIG. 8 is an image of cerebral ischemia in a rat brain.

[0041]FIG. 9 is an image showing the circulation of CSF in the brain.

[0042]FIG. 10 is a graph showing inosine release from a composition ofthe invention.

DETAILED DESCRIPTION OF THE INVENTION

[0043] The blood brain barrier (BBB) presents the primary obstacle indelivering drugs to the brain. The BBB is composed of small bloodcapillaries lined with specialized endothelial cells. These smallcapillaries form the terminal branches of a vast network of bloodvessels that deliver blood to the brain. The BBB's main purpose is toprevent pathogens from entering the CNS. The BBB prevents drugs fromentering the CNS based on molecular weight, lipid solubility, and degreeof ionization. Pharmaceutical companies have made numerous attempts toby-pass or force drugs through the BBB. These attempts include thedisruption of the BBB by chemicals, intrathecal delivery using infusionpumps, direct delivery to the CSF through implantation of geneticallyengineered cells and transplantation of fetal neural tissue. Each ofthese methods causes undesirable side effects, as evidenced by toxicside effects, dimensional complications, lack of reliability and highcost.

[0044] Many drugs exist which pass the BBB and are therefore suitablefor the treatment of certain disorders of the central nervous system(CNS). However, it has been difficult to get an adequate concentrationof drug into the small blood capillaries that make up the BBB withoutunwanted side effects, as well as in the proper time frame necessary toeffectively treat neurological diseases. In addition, there are a numberof additional drugs which have potential clinical usefulness, but thatdo not pass through the BBB. Unfortunately, to effectively treatneurological diseases with drugs being delivered via the bloodstream,the drugs must be designed to penetrate the BBB. It is thereforedesirable to develop methods to deliver drugs directly to the CNS andeven to a targeted area within.

[0045] The compositions and methods of the invention provide a solutionto earlier problems in delivering drugs to brain tissues becausethey: 1) are capable of local delivery to a targeted area such as thebrain, spinal column and related tissues; 2) protect therapeutic agentsfrom degrading to quickly; and 3) release therapeutic agents in asustained manner.

[0046] The polymer compositions of the invention are biodegradable,non-toxic, and provide sustained delivery of therapeutic agents at anarea of interest within the central nervous system (CNS). The inventiondiffers from existing technologies in several ways: the polymercomposition is fabricated from biodegradable materials and providessustained delivery of at least one therapeutic agents over an extendedtime period up to several months; the site of placement of thecomposition is in the cerebrospinal fluid and the device is used totreat acute, traumatic neurological disorders with rapid onset of apathologic sequence leading to cell death. Current polymeric devices forthe CNS are centered on clinical targets that require implantation intoa specific part of the brain parenchyma while drug is delivered over along period of time (several months to years) to abate certainneuro-degenerative disorders (Harbaugh R. E., Intracranial DrugAdministration in Alzheimer's Disease. Psychopharmacology Bulletin22(1), 1986; Winn S. R. et. al., Rats. Exp. Neuro 105: 244- 250, 1989;Langer R., Brain. J. Cont. Rei., 16: 53-60, 1991; Brem H. et al. J.Neurosurg 74: 441-46, 1991; Camarata P. J. et al., Neurosurgery, 30(3):313-19, 1992; Menei P. et al., Neurosurgery, 34(6):1058-64 1994).

[0047] The compositions of the invention have all of the above-describeddesirable properties while, at the same time having the unique propertyof being controllably buoyant in cerebrospinal fluid (CSF). This uniqueproperty is accomplished by the addition of at least one buoyancy agentto the polymer composition at the time of manufacture. The buoyancyagent confers properties that allow for targeting of the compositions toor away from the brain or the spinal cord (the top or the bottom of theCNS) or within the CSF for local delivery of therapeutic agents. As theCSF circulates through the subarachnoid space and ventricles of thebrain, indicated by the arrows in FIG. 9, the polymer biodegradesallowing the therapeutic agent to be released into the extracellularspace of the brain on a controlled and sustained basis. The polymer alsoserves to protect the therapeutic agent from premature degradation.

[0048] The compositions of the invention can be made: negatively buoyant(having a specific gravity that is greater than that of CSF), neutrallybuoyant (having a specific gravity that is about equal to CSF), orpositively buoyant (having a specific gravity that is less than that ofCSF). The specific gravity (SG) of CSF is normally about 1.0063 gm/ml toabout 1.0075 gm/ml, although those skilled in the art will recognizethat the specific gravity of CSF may vary individually between subjects.

[0049] Currently, intrathecal pump delivery to administer pain medicineconsists of a pump and catheter, both of which are surgically placedunder the skin. A catheter connects to the pump and is tunneled underthe skin to the site where medication is to be delivered. The pumpreleases the medication at the set rate, and the medication flows fromthe pump, through the catheter to the site of delivery in theintrathecal space. Intrathecal drug delivery has its drawbacks.Implanting a pump is not an inocuous procedure. It causes significantcosmetic alteration at the implant site that makes it unacceptable tomany patients. The pump is a mechanical device that is prone to problemsranging from glitches and mechanical compromise, to total mechanicalfailure. Rare instances of catheter tip granulomas can cause significantneurological symptoms. The patient is dependent on refills of drugs andadjustment of the pump to the few professionals and deliveryorganizations available to do this and expertise is still developing.While implantable pumps have been proven effective, they are not likelyto be widely prescribed for humans because of infection risk and tissuedamage caused by accidental movement of the pump and catheter. If apatient with a pump is in an accident, the pump can stop working and thecatheter can be displaced. Emergency room physicians and personnel areusually not well versed in how to deal with pump patients.

[0050] The compositions of the invention are administered byintraventricular, intrathecal or epidermal administration. Theadvantages of intrathecally delivering the compositions of the inventionover i.v. or oral administration include: 1) the BBB is bypassedpreventing systemic toxic side effects and guaranteeing that thetherapeutic agent will reach the damaged brain tissue, 2) the polymerserves to protect the therapeutic agent from breaking down prematurely,3) the therapeutic agent is released continuously from the polymer intothe CSF allowing the damaged tissue to be treated over an extended timeperiod and 4) multiple therapeutic agents can be administered anddelivered simultaneously for purposes of combinational therapy. Forexample, antioxidants, NMDA antagonists, etc can be used.

[0051] In a preferred embodiment, the compositions are administeredintrathecally via a needle either using a single “one shot” lumbarpuncture (LP) or a single “one shot” cisternal puncture (CP) making itmore desirable to patients as compared to intrathecal pump delivery. Asthe polymer composition degrades, the therapeutic agent is releasedslowly over time. The polymer composition also protects the therapeuticagent from premature degradation.

[0052] The compositions of the invention are easily suspended in aqueousvehicles and injected through conventional hypodermic needles. Prior toinjection, the carriers can be sterilized with, preferably, gammaradiation or electron beam sterilization.

[0053] Those skilled in the art will recognize that for certain centralnervous system disorders, there may be an increase in intracranialpressure (ICP), causing the force and/or weight of the circulating “CSF”to push against the meningeal membranes within which the “CSF” flows.This could have an effect on the administration of the polymercompositions of the invention, and therefore it may be necessary to:administer the polymer compositions through a shunt that is used torelieve intracranial pressure, perform a lumbar puncture (LP) to removean equal volume of CSF to the volume of polymer composition to beadministered, and to elevate the head and neck/upper torso to alleviatethe extra pressure.

[0054] The appropriate dose of the therapeutic agent is that amounteffective to prevent occurrence of the symptoms of the disorder or totreat some symptoms of the disorder from which the subject suffers. By“effective amount”, “therapeutic amount” or “effective dose” is meantthat amount sufficient to elicit the desired pharmacological ortherapeutic effects, thus resulting in effective prevention or treatmentof the disorder. Thus, when treating a CNS disorder, an effective amountof a therapeutic agent is an amount sufficient to pass across the BBB ofthe subject. Prevention of the disorder is manifested by delaying theonset of the symptoms of the disorder. Treatment of the disorder ismanifested by a decrease in the symptoms associated with the disorder oran amelioration of the recurrence of the symptoms of the disorder.

[0055] The effective dose can vary, depending upon factors such as thecondition of the subject, the severity of the symptoms of the disorder,and the manner in which the composition is administered. The effectivedose of therapeutic agents will of course differ from subject to subjectbut in general includes amounts starting where CNS effects or otherdesired therapeutic effects occur, but below the amount where musculareffects are observed.

[0056] Typically, the effective dose of therapeutic agents generallyrequires administering the therapeutic agent in an amount of less than 5mg/kg of subject weight. Often, the therapeutic agents of the presentinvention are administered in an amount from 1 mg to less than 100 μg/kgof subject weight, frequently between about 10 μg to less than 100 μg/kgof subject weight, and preferably between about 10 μg to about 50 μg/kgof subject weight. The foregoing effective doses typically representthat amount administered as a single dose, or as one or more dosesadministered over a 24-hour period.

[0057] For human subjects, the effective dose of typical therapeuticagents generally requires administering the therapeutic agent in anamount of at least about 1, often at least about 10, and frequently atleast about 25 μg/24 hr./subject. For human subjects, the effective doseof typical therapeutic agents requires administering the agent whichgenerally does not exceed about 500, often does not exceed about 400,and frequently does not exceed about 300 μg/24 hr./subject. In addition,administration of the effective dose is such that the concentration ofthe therapeutic agent within the plasma of the subject normally does notexceed 500 ng/ml, and frequently does not exceed 100 ng/ml.

[0058] The therapeutic agents useful according to the compositions andmethods of the present invention have the ability to pass across theblood brain barrier of the subject. As such, such therapeutic agentshave the ability to enter the central nervous system of the subject. Thelog P values of typical therapeutic agents, which are useful in carryingout the present invention are generally greater than about 0, often aregreater than about 0.5, and frequently are greater than about 1. The logP values of such typical compounds generally are less than about 3.5,often are less than about 3, and sometimes are less than about 2.5. LogP values provide a measure of the ability of a therapeutic agent to passacross a diffusion barrier, such as a biological membrane. See, Hansch,et al., J. Med. Chem. 11:1 (1968).

[0059] Therapeutic agents of the present invention, when employed ineffective amounts in accordance with the compositions and methods of theinvention, are effective towards providing some degree of prevention ofthe progression of CNS disorders, amelioration of the symptoms of CNSdisorders, and amelioration to some degree of the recurrence of CNSdisorders. However, such effective amounts of those therapeutic agentsare not sufficient to elicit any appreciable side effects, as isdemonstrated by decreased effects on preparations believed to reflecteffects on the cardiovascular system, or effects to skeletal muscle. Assuch, administration of therapeutic agents of the present inventionprovides a therapeutic window in which treatment of certain CNSdisorders is provided, and side effects are avoided. That is, aneffective dose of a therapeutic agent of the present invention issufficient to provide the desired effects upon the CNS, but isinsufficient (i.e., is not at a high enough level) to provideundesirable side effects. Preferably, effective administration of atherapeutic agent of the present invention resulting in treatment of CNSdisorders occurs upon administration of less ⅓, frequently less than ⅕,and often less than {fraction (1/10)}, that amount sufficient to causeany side effects to a significant degree.

[0060] Polymers of the invention are naturally derived polymers, such asalbumin, alginate, cellulose derivatives, collagen, fibrin, gelatin, andpolysaccharides as well as synthetic polymers such as polyesters (PLA,PLGA), polyethylene glycol, poloxomers, polyanhydrides, polyorthoestersand pluronics. Polymers are designed to be flexible; the distancebetween the bioactive sidechains and the length of a linker between thepolymer backbone and the group can be controlled. Other suitablepolymers and methods for their preparation are described in U.S. Pat.Nos. 5,455,044 and 5,576,018.

[0061] Naturally derived polymers, such as alginate, are also used todeliver living therapeutic agents or agents that break down/become lesseffective as part of the manufacturing process such as bone marrow cellsor fetal neural tissue or stem cells for stroke recovery because oftheir non-toxic make-up. Similarly, they can be used to absorb toxicsubstances such as calcium released in an ischemic cascade to be brokendown by encapsulated calcium consuming enzymes.

[0062] The earliest of these polymers were originally intended forother, nonbiological uses, and were selected because of their desirablephysical properties, for example: Poly(urethanes) for elasticity;Poly(siloxanes) or silicones for insulating ability; Poly(methylmethacrylate) for physical strength and transparency; Poly(vinylalcohol) for hydrophilicity and strength; Poly(ethylene) for toughnessand lack of swelling; and Poly(vinyl pyrrolidone) for suspensioncapabilities.

[0063] To be successfully used in controlled drug delivery formulations,a material must be chemically inert and free of leachable impurities. Itmust also have an appropriate physical structure, with minimal undesiredaging, and be readily processable. Some of the materials that arecurrently being used or studied for controlled drug delivery include:Poly(2-hydroxy ethyl methacrylate); Poly(N-vinyl pyrrolidone);Poly(methyl methacrylate); Poly(vinyl alcohol); Poly(acrylic acid);Polyacrylamide; Poly(ethylene-co-vinyl acetate); Poly(ethylene glycol);and Poly(methacrylic acid).

[0064] However, in recent years additional polymers designed primarilyfor medical applications have entered the arena of controlled release.Many of these materials are designed to degrade within the body, amongthem: Polylactides (PLA); Polyglycolides (PGA);Poly(lactide-co-glycolides) (PLGA); Polyanhydrides; Polyorthoesters.

[0065] Factors affecting biodegradation of polymers, such asphysicochemical factors (ion exchange, ionic strength, pH), will haveutility. For example, when ions are released during a stroke or TBI(cerebral ischemia) certain polymers in a dose can be triggered torelease their load. Some of the physicochemical factors affecting thebiodegradation of the polymers include: chemical structure; chemicalcomposition; distribution of repeat units in multimers; presence ofionic groups; presence of unexpected units or chain defects;configuration structure; molecular weight; molecular-weightdistribution; morphology (amorphous/semicrystalline, microstructures,residual stresses); presence of low-molecular-weight compounds;processing conditions; annealing; sterilization process; storagehistory; shape; site of implantation; adsorbed and absorbed compounds(water, lipids, ions, etc.); physical factors (shape and size changes,variations of diffusion coefficients, mechanical stresses, stress- andsolvent-induced cracking, etc.); and the mechanism of hydrolysis(enzymes versus water).

[0066] In a preferred embodiment, the polymer used is apoly(lactide-co-glycolide) copolymer (PLGA). The Food and DrugAdministration has approved products made of PLGA (i.e. Lupron Depot®).Even more importantly, PLGA has shown to be non-toxic when placed in theCNS. PLGA is soluble in organic solvents. PLGA degrades by bulkhydrolysis in water as a function of the lactide:glycolide ratio andmolecular weight (Langer R. et al., Chemical and physical structure ofpolymers as carriers for controlled release of therapeutic agents: areview, JMS-Rev. Macromol. Chem. Phys., 23: 61-126, 1983; Gopferich A.,Polymer bulk erosion., Macromolecules 30: 2598-2604, 1997.) The rate ofPLGA hydrolysis controls the rate of release of an encapsulatedpharmaceutical. Thus, one can control the release of a drug in a PLGApolymer matrix by varying PLGA's lactide:glycolide ratio and molecularweight. Also, by controlling various process parameters (i.e.solvent/non-solvent systems, shear rate during emulsification orhardening) it is possible to control the size of the microspheres madefrom the PLGA/drug matrix.

[0067] The compositions of the invention preferably contain at least0.1% of polymer by weight. The percentage of the compositions may, ofcourse, be varied and may conveniently be between about 2 to about 80%of the weight and preferably 2 to about 10% of a given unit dosage form.The amount of polymer in such therapeutically useful compositions issuch that an effective dosage level will be obtained.

[0068] Therapeutic Agents

[0069] As discussed above, the polymer compositions of the invention areused for sustained delivery of at least one therapeutic agent. A widevariety of therapeutic agents are included in the compositions andmethods of the invention, including, but not limited to ADHD drugs(methylphenidate & SR, Dexedrine & spansules, adderall, adderall XR,concerta, strattera), alkaloids, alkylating agents, alpha-2-adrenergicagonists, AMPA receptor antagonists (NBQX), amino acids, analgesics,androgens, angiogenesis inhibitors, anti-anxiety drugs, antibiotics,anticoagulants (ancrod), anti-convulsants (phenobarbital, dilantin,primidone, tegretol & XR, carbatrol, lamictal, gabitril, depakote & ER,keppra, neurontin, topamax, zarontin, trileptal), anti-depressants(amitriptyline, amoxapine, clomipramine, desipramine, doxepin,imipramine, nortriptyline, trazodone, fluxetine, lexapro, effexor,effexor XR, paxil, paxil CR, remeron sol tab, serzone, Zoloft,wellbutrin & SR), anti-emitics, anti-epileptic medications,antiestrogens, anti-inflammatory agents, anti-mania drugs,anti-metabolites, anti-panic drugs, anti-parkinson drugs (selegiline,trihexyphenidyl, bromocriptine, sinemet & CR, mirapex, requip, permax),antipsychotics (phenothiazines, thioxanthene, dibenzodiazepines,benzisoxazole, butyrophenones, indolone, diphenylbutylpiperidine),anti-psychotropic agents, antipyretics, anti-tremor drugs,antiandrogens, antibodies, antiangiogenic facots, antioxidants(superoxide dismutase (SOD), catalase, nitric oxide, mannitol),Apha-synuclein inhibitors apoptosis blockers, barbituates, bcl-2oncogene products, beta-amyloid inhibitors, calcium channel blockers(isradipine, nicardipine, nifedipine, nimodipine, verapamil,ziconotide), calpain inhibitors, carbidopa, cardiac anti-arrhythmics,caspase inhibtors, central alpha-2 agonists, chemotherapy drugs(mechlorethamine, vincristine, procarbazine, prednisone, doxorubicin,bleomycin, vinblastine, dacarbazine), choline, cholinergic neuronotropicagents, crystalline alkaloids, local anesthetics, antihypertensivedrugs, collagen synthesis inhibitor, cytokine regulator fibroblastblocker, cluster-blocking drugs, CNS mood stabilizers (lithium, eskalithCR, depakote, corticosteroids, cyclooxygenase (COX)-2 inhibitors,cytokines, cytostatic drugs, cytotoxic drugs, enzymes, epidermals,epipodophyllotoxins, estrogens, ethylene imines and methyl-melamines,excitatory amino acid antagonist or agonist, extracellular matrixproteins, folic acid analogs, free radical scavengers, gangliosides,genes, gene transcription regulators, gonadotropin-releasing hormoneanalogs, hematological agents, hormones, IL-1 receptor inhibitors,immunomodulators, initoxantrone, lipid peroxidation inhibitors, livingcells such as bone marrow cells or fetal neural tissue or stem cells,metal co-ordination complexes and mixtures thereof, minerals, mineralsupplements, monoamine agonists (amphetamines), monoamine oxidaseinhibitors (MAOIs), mutant gene expression suppressors (smallinterfering RNA), myelin-associated neurite growth inhibitor blocker,natural anticancer products, nerve growth enhancing agents,neuroleptics, neurotransmitters (dopamine, dopamine agonists, serotonin,norepinephrine, epinephrine, histamine, acetylcholine,gamma-aminobutyric acid (GABA), glycine, glutamate, aspartate, nitricoxide (NO), carbon monoxide), neurotrophic factors (endorphins,citicholine, inosine), N-methyl-D-aspartate (NMDA) antagonists(dextrorphane, MK-801, agmatine, GK-11), neurotrophic drugs (IGF-1),neurotrophins (NGF, GDNF, CNTF, NT-3, NT-4/5, FGF, BDNF), nicotinicacetylcholine receptor (nAChR) agonists, nitrogen mustards, nitrosoureas, nitric oxide inhibitor, non-benzodiazepine anxiolytics andhypnotics, nonsteroidal anti-inflammatory drugs (NSAIDS: aspirin,acetaminophen, choline magnesium trisalicylate, diclofenac, diflunisal,fenoprofen, flurbiprofen, ibuprofen, IN-1 antibody, indomethacin,ketoprofen, meclofenamate, nabumetone, naproxen, oxaprozin,phenylbutazone, piroxicam, salsalate, sulindac, tolmetin), omega 3 oils,opioid analgesics, peptides and proteins derived from venom andassociated derivatives (conopeptides, platinum complexes and mixturesthereof, potassium channel blockers (4-AP), protease inhibitors,proteosome inhibitors, purine analogs, pyrimidine analogs,radiopharmaceuticals, serotonin reuptake inhibitors (SSRIs), signaltransduction modulators, skeletal muscle relaxants, sodium channelblockers, steroid anti-inflammatory drugs (cortisone, prednisone,prednisolone, dexamethasone), tetramethylpyrazine, toxic alpha-synucleinproduction inhibitors, tricyclic antidepressants (TCAs), trophicfactors, vinca alkaloids, vitamins (such as vitamin A, vitamin B,vitamin C, vitamin D, vitamin E, and vitamin K), nerve growth factors,glycoproteins, phosphodiesterase (PDE) type 4 inhibitor, beta-agonists,cholinesterase inhibitors (Tacrine, Donepezil), monosaccharides,interferon, herbs, anti-virals, neuroactive polyunsaturated lipids(NPLs), bile molecules, GABA reuptake inhibitor, carbonic anhydraseinhibitor, Valproic acid derivatives, imidazolins, ceramide inhibitors,arginase inhibitors, cephalon derivatives, polyamine inhibitors, IFN-γinhibitor, arginase I and II inhibitor, DNA synthesis inhibitors,statins, nicotine.

[0070] Preferred therapeutic agents for use in the compositions andmethods of the invention include, inosine, citicholine, SOD, anddextrorphan.

[0071] In addition to the therapeutic agent and the pharmaceuticallyacceptable polymer, the compositions of the invention can compriseadditional pharmaceutically acceptable carriers and/or excipients.

[0072] Central Nervous System Disorders

[0073] The compositions and methods of the invention are used to preventand/or treat many central nervous system disorders including, but notlimited to, ADD, ADHD, AIDS—Neurological Complications, Absence of theSeptum Pellucidum, Acquired Epileptiform Aphasia, Acute DisseminatedEncephalomyelitis, Adrenoleukodystrophy, Agenesis of the CorpusCallosum, Agnosia, Aicardi Syndrome, Alexander Disease, Alpers' Disease,Alternating Hemiplegia, Alzheimer's Disease, Amyotrophic LateralSclerosis, Anencephaly, Aneurysm, Angelman Syndrome, Angiomatosis,Anoxia, Aphasia, Apraxia, Arachnoid Cysts, Arachnoiditis, Arnold-ChiariMalformation, Arteriovenous Malformation, Aspartame, Asperger Syndrome,Ataxia Telangiectasia, Ataxia, Attention Deficit-Hyperactivity Disorder,Autism, Autonomic Dysfunction, Back Pain, Barth Syndrome, BattenDisease, Behcet's Disease, Bell's Palsy, Benign Essential Blepharospasm,Benign Focal Amyotrophy, Benign Intracranial Hypertension,Bernhardt-Roth Syndrome, Binswanger's Disease, Blepharospasm,Bloch-Sulzberger Syndrome, Brachial Plexus Birth Injuries, BrachialPlexus Injuries, Bradbury-Eggleston Syndrome, Brain Aneurysm, BrainInjury, Brain and Spinal Tumors, Brown-Sequard Syndrome, BulbospinalMuscular Atrophy, Canavan Disease, Carpal Tunnel Syndrome, Causalgia,Cavernomas, Cavernous Angioma, Cavernous Malformation, Central CervicalCord Syndrome, Central Cord Syndrome, Central Nervous System Lymphoma,Central Pain Syndrome, Cephalic Disorders, Cerebellar Degeneration,Cerebellar Hypoplasia, Cerebral Aneurysm, Cerebral Arteriosclerosis,Cerebral Atrophy, Cerebral Beriberi, Cerebral Gigantism, CerebralHypoxia, Cerebral Ischemia, Cerebral Palsy, Cerebro-Oculo-Facio-SkeletalSyndrome, Charcot-Marie-Tooth Disorder, Chiari Malformation, Chorea,Choreoacanthocytosis, Chronic Inflammatory Demyelinating Polyneuropathy(CIDP), Chronic Orthostatic Intolerance, Chronic Pain, Coffin LowrySyndrome, Coma, including Persistent Vegetative State, Complex RegionalPain Syndrome, Congenital Facial Diplegia, Congenital Myasthenia,Congenital Myopathy, Congenital Vascular Cavernous Malformations,Corticobasal Degeneration, Cranial Arteritis, Craniosynostosis,Creutzfeldt-Jakob Disease, Cumulative Trauma Disorders, Cushing'sSyndrome, Cytomegalic Inclusion Body Disease (CIBD), CytomegalovirusInfection, Dancing Eyes-Dancing Feet Syndrome, Dandy-Walker Syndrome,Dawson Disease, De Morsier's Syndrome, Dejerine-Klumpke Palsy,Dementia—Multi-Infarct, Dementia—Subcortical, Dementia With Lewy Bodies,Dermatomyositis, Developmental Dyspraxia, Devic's Syndrome, DiabeticNeuropathy, Diffuse Sclerosis, Dysautonomia, Dysgraphia, Dyslexia,Dysphagia, Dyspraxia, Dystonias, Early Infantile EpilepticEncephalopathy, Empty Sella Syndrome, Encephalitis Lethargica,Encephalitis and Meningitis, Encephaloceles, Encephalopathy,Encephalotrigeminal Angiomatosis, Epilepsy, Erb's Palsy, Erb-Duchenneand Dejerine-Klumpke Palsies, Fabry's Disease, Fahr's Syndrome,Fainting, Familial Dysautonomia, Familial Hemangioma, FamilialIdiopathic Basal Ganglia Calcification, Familial Spastic Paralysis,Febrile Seizures, Fisher Syndrome, Floppy Infant Syndrome, Friedreich'sAtaxia, Gaucher's Disease, Gerstmann's Syndrome,Gerstmann-Straussler-Scheinker Disease, Giant Cell Arteritis, Giant CellInclusion Disease, Globoid Cell Leukodystrophy, GlossopharyngealNeuralgia, Guillain-Barre Syndrome, HTLV-1 Associated Myelopathy,Hallervorden-Spatz Disease, Head Injury, Headache, Hemicrania Continua,Hemifacial Spasm, Hemiplegia Alterans, Hereditary Neuropathies,Hereditary Spastic Paraplegia, Heredopathia Atactica Polyneuritiformis,Herpes Zoster Oticus, Herpes Zoster, Hirayama Syndrome,Holoprosencephaly, Huntington's Disease, Hydranencephaly, Hydrocephalus,Hydromyelia, Hypercortisolism, Hypersomnia, Hypertonia, Hypotonia,Hypoxia, Immune-Mediated Encephalomyelitis, Inclusion Body Myositis,Incontinentia Pigmenti, Infantile Hypotonia, Infantile Phytanic AcidStorage Disease, Infantile Refsum Disease, Infantile Spasms,Inflammatory Myopathy, Intestinal Lipodystrophy, Intracranial Cysts,Intracranial Hypertension, Isaac's Syndrome, Joubert Syndrome,Kearns-Sayre Syndrome, Kennedy's Disease, Kinsbourne syndrome,Kleine-Levin syndrome, Klippel Feil Syndrome, Klippel-Trenaunay Syndrome(KTS), Klüver-Bucy Syndrome, Korsakoff's Amnesic Syndrome, KrabbeDisease, Kugelberg-Welander Disease, Kuru, Lambert-Eaton MyasthenicSyndrome, Landau-Kleffner Syndrome, Lateral Femoral Cutaneous NerveEntrapment, Lateral Medullary Syndrome, Learning Disabilities, Leigh'sDisease, Lennox-Gastaut Syndrome, Lesch-Nyhan Syndrome, Leukodystrophy,Levine-Critchley Syndrome, Lewy Body Dementia, Lissencephaly, Locked-InSyndrome, Lou Gehrig's Disease, Lupus—Neurological Sequelae, LymeDisease—Neurological Complications, Machado-Joseph Disease,Macrencephaly, Megalencephaly, Melkersson-Rosenthal Syndrome,Meningitis, Menkes Disease, Meralgia Paresthetica, MetachromaticLeukodystrophy, Microcephaly, Migraine, Miller Fisher Syndrome,Mini-Strokes, Mitochondrial Myopathies, Mobius Syndrome, MonomelicAmyotrophy, Motor Neuron Diseases, Moyamoya Disease, Mucolipidoses,Mucopolysaccharidoses, Multi-Infarct Dementia, Multifocal MotorNeuropathy, Multiple Sclerosis, Multiple System Atrophy with PosturalHypotension, Multiple System Atrophy, Muscular Dystrophy,Myasthenia—Congenital, Myasthenia Gravis, Myelinoclastic DiffuseSclerosis, Myoclonic Encephalopathy of Infants, Myoclonus,Myopathy—Congenital, Myopathy—Thyrotoxic, Myopathy, Myotonia Congenita,Myotonia, Narcolepsy, Neuroacanthocytosis, Neurodegeneration with BrainIron Accumulation, Neurofibromatosis, Neuroleptic Malignant Syndrome,Neurological Complications Of Lyme Disease, Neurological Complicationsof AIDS, Neurological Manifestations of Pompe Disease, NeurologicalSequelae Of Lupus, Neuromyelitis Optica, Neuromyotonia, Neuronal CeroidLipofuscinosis, Neuronal Migration Disorders, Neuropathy—Hereditary,Neurosarcoidosis, Neurotoxicity, Nevus Cavernosus, Niemann-Pick Disease,O'Sullivan-McLeod Syndrome, Occipital Neuralgia, Occult SpinalDysraphism Sequence, Ohtahara Syndrome, Olivopontocerebellar Atrophy,Opsoclonus Myoclonus, Orthostatic Hypotension, Overuse Syndrome,Pain—Chronic, Paraneoplastic Syndromes, Paresthesia, Parkinson'sDisease, Parmyotonia Congenita, Paroxysmal Choreoathetosis, ParoxysmalHemicrania, Parry Romberg, Pelizaeus-Merzbacher Disease, Pena Shokeir IISyndrome, Perineural Cysts, Periodic Paralyses, Peripheral Neuropathy,Periventricular Leukomalacia, Persistent Vegetative State, PervasiveDevelopmental Disorders, Phytanic Acid Storage Disease, Pick's Disease,Pinched Nerve, Piriformis Syndrome, Pituitary Tumors, Polymyositis,Pompe Disease, Porencephaly, Post-Polio Syndrome, PostherpeticNeuralgia, Postinfectious Encephalomyelitis, Postural Hypotension,Postural Orthostatic Tachycardia Syndrome, Postural TachycardiaSyndrome, Primary Lateral Sclerosis, Prion Diseases, ProgressiveHemifacial Atrophy, Progressive Locomotor Ataxia, Progressive MultifocalLeukoencephalopathy, Progressive Sclerosing Poliodystrophy, ProgressiveSupranuclear Palsy, Pseudotumor Cerebri, Ramsay Hunt Syndrome Type I,Ramsay Hunt Syndrome Type II, Rasmussen's Encephalitis, ReflexSympathetic Dystrophy Syndrome, Refsum Disease—Infantile, RefsumDisease, Repetitive Motion Disorders, Repetitive Stress Injuries,Restless Legs Syndrome, Retrovirus-Associated Myelopathy, Rett Syndrome,Reye's Syndrome, Riley-Day Syndrome, SUNCT Headache, Sacral Nerve RootCysts, Saint Vitus Dance, Salivary Gland Disease, Sandhoff Disease,Schilder's Disease, Schizencephaly, Seizure Disorder, Septo-OpticDysplasia, Shaken Baby Syndrome, Shingles, Shy-Drager Syndrome,Sjogren's Syndrome, Sleep Apnea, Sleeping Sickness, Soto's Syndrome,Spasticity, Spina Bifida, Spinal Cord Infarction, Spinal Cord Injury,Spinal Cord Tumors, Spinal Muscular Atrophy, Spinocerebellar Atrophy,Steele-Richardson-Olszewski Syndrome, Stiff-Person Syndrome,Striatonigral Degeneration, Stroke, Sturge-Weber Syndrome, SubacuteSclerosing Panencephalitis, Subcortical Arteriosclerotic Encephalopathy,Swallowing Disorders, Sydenham Chorea, Syncope, Syphilitic SpinalSclerosis, Syringohydromyelia, Syringomyelia, Systemic LupusErythematosus, Tabes Dorsalis, Tardive Dyskinesia, Tarlov Cysts,Tay-Sachs Disease, Temporal Arteritis, Tethered Spinal Cord Syndrome,Thomsen Disease, Thoracic Outlet Syndrome, Thyrotoxic Myopathy, TicDouloureux, Todd's Paralysis, Tourette Syndrome, Transient IschemicAttack, Transmissible Spongiform Encephalopathies, Transverse Myelitis,Traumatic Brain Injury (TBI), Tremor, Trigeminal Neuralgia, TropicalSpastic Paraparesis, Tuberous Sclerosis, Vascular Erectile Tumor,Vasculitis including Temporal Arteritis, Von Economo's Disease, VonHippel-Lindau disease (VHL), Von Recklinghausen's Disease, Wallenberg'sSyndrome, Werdnig-Hoffman Disease, Wernicke-Korsakoff Syndrome, WestSyndrome, Whiplash, Whipple's Disease, Williams Syndrome, Wilson'sDisease, X-Linked Spinal and Bulbar Muscular Atrophy, ZellwegerSyndrome. See National Institute of Neurological Disorders and Strokewebsite.

[0074] Central nervous system (CNS) lymphoma is defined as lymphomalimited to the cranial-spinal axis without systemic disease. Vincaalkaloids and other plant products, cytostatic drugs, cytotoxic drugs,hormones (estrogens and anti-estrogens), alkylating agents,immunomodulators (immunostimulators and immunosuppressives),hematological agents, non-steroidal products, radiopharmaceuticals,antibodies, antiandrogens, and epidermals are just a number oftherapeutic agents that can be delivered to target tissues in the CNSusing the polymer compositions described herein.

[0075] Additionally, neurotrophic substances play a number of potentialtherapeutic roles in other neurological disorders. One of the mechanismsby which the brain repairs itself following brain damage is through theregeneration and sprouting of new neuronal connections. It has recentlybeen shown that injections of growth promoting, neurotrophic substances,or more specifically purine nucleosides such as inosine or guanosine,enhance the rate and extent of regeneration in the brain, also known asaxonal outgrowth, and bring about an enhanced degree of behavioralrecovery in brain damaged animals and likely, mammals including humans.

[0076] TBI and Stroke

[0077] Traumatic Brain Injury (TBI), and Stroke are CNS disorders thatare characterized by the need for immediate short-term drug therapy.Traumatic Brain Injury (TBI) is caused primarily by a traumatic blow tothe head causing damage to the brain, often without penetrating theskull. The initial trauma can result in expanding hematoma, subarachnoidhemorrhage (increase in blood volume), cerebral edema (increase ininterstitial fluid volume), raised intracranial pressure (ICP), andcerebral hypoxia, which can, in turn, lead to severe secondary eventsdue to low cerebral blood flow (CBF). Half of the people with TBI diebefore reaching the hospital and from those that survive, a largepercentage suffer serious neurological disorders. There is not much thatmodern medicine can do to prevent or minimize the initial damage causedby TBI. Instead, doctors invest time trying to prevent secondary braininjury and, after the patient's health stabilizes, rehabilitate theinjuries.

[0078] Stroke is the destruction of brain tissue due to impaired bloodsupply (cerebral ischemia) caused by intracerebral hemorrhage (increasein blood volume), thrombosis (clotting), or embolism (obstruction causedby clotted blood or other foreign matter circulating in thebloodstream). Stroke is the third commonest cause of death in the UnitedStates. The deleterious effects of a stroke are comparable to thosecaused by TBI.

[0079] Many therapeutic agents exist today for the treatment of centralnervous system (CNS) disorders including Traumatic Brain Injury (TBI),and Stroke. These include: (a) nonsteroidal anti-inflammatory agents(aspirin, acetaminophen, indomethacin, ibuprofen), (b) steroidanti-inflammatory agents (cortisone, prednisone, prednisolone,dexamethasone), (c) antioxidants (superoxide dismutase, catalase, nitricoxide, mannitol), (d) calcium channel blockers (nimodipine, nifedipine,verapamil, nicardipine, isradipine), and (e) neurotrophic factors(endorphins, citicholine).

[0080] This invention provides compositions and methods which areapplied to the large clinical population suffering from CNS disorders.The pathologic sequence of events that lead to debilitating aspects ofTBI and stroke are effectively treated via this protocol. Preferably,the encapsulated therapeutic agents described herein are administered tothe subject in the period from the time of injury to 100 hours,preferably within 1, 2, 10, 20, or 24 hours, and more preferably within6 to 12 hours after the traumatic brain injury (TBI) or stroke hasoccurred.

[0081] Cerebral ischemia resulting from stroke or TBI is generallyunderstood as a sequence of events (ischemic cascade) arising from ablood clot or trauma that depletes the brain of blood, oxygen, andglucose by cutting off the blood supply to a core region of brain. Cellsin the core region (infarct zone) die regardless of interventionaltherapy (See FIG. 8). Cells on the periphery of the core region (thepenumbra) are targeted for drug therapies because they are not injuredas a result of the original trauma, however are at high risk from theischemic cascade following the initial event. The therapeutic goal inacute stroke intervention has been aimed at salvaging the cells in thepenumbra region, thus limiting the overall brain damage. Cells in theaffected area cannot function and begin to die within minutes. Theresults range from mild neurological impairment, to paralysis, and evendeath.

[0082] Recent studies suggest that lowering the body temperatureslightly within a few hours of having a stroke can reduce brain damageand risk of death. In these studies, fully conscious patients in whommodest hypothermia was achieved via surface cooling had a six-monthsurvival rate nearly twice that of untreated control patients. SeeKammersgaard et al., Stroke, 31(9):2251 (2000). Therefore, it may bedesirable to administer the compositions of the invention withhypothermia, for treatment of stroke. For example, hypothermia can beinduced before, after, or in conjunction with administration of thecompositions of the invention. The compositions may contain more thanone therapeutic agent that can be encapsulated in separate polymercompositions, or in the same polymer composition as described herein.

[0083] In certain conditions, such as hydrocephalus and edema, it may benecessary to insert a shunt to control pressure. The compositions of theinvention can be administered before, after, or during shunt procedure.Those skilled in the art will recognize that the compositions of theinvention can be administered before, after, or during other surgicalinterventions.

[0084] Combination therapy or delivery of “drug cocktails” leads toimproved treatment for certain traumatic CNS injuries. In a preferredembodiment, the methods of the invention are used to treat a subjectsuffering from stroke. In another preferred embodiment, the method ofthe invention is used to treat a subject suffering from Traumatic BrainInjury (TBI). Depending upon the disease to be treated, it may beadvantageous to provide more than one composition of the invention tothe central nervous system. For example, a single composition maycontain more than one therapeutic agent or a plurality of compositionscontaining different therapeutic agents may be co-administered. Also, asubject suffering from more then one central nervous system disorder istreated by the compositions of the invention.

[0085] The combination drug therapy is carried out early (from minutes(1, 2, 5, 10, 30, 45, or 60 minutes) to 3-4 hours after stroke or TBI)to late (days (1, 2, 5, or 7 days) or weeks (1, 2, 5, 7, 14, 40, or 24weeks) after stroke or TBI) relative to the duration of the ischemiccascade.

[0086] Inosine

[0087] Inosine, a purine nucleoside, is a naturally occurring by-productof Adenosine. Inosine enters cells via facilitated diffusion or can besynthesized readily from Adenosine. In at least some neurons, inosineactivates an intracellular signaling pathway that regulates theexpression of multiple genes involved in axon outgrowth. Benowitz etal., J. Biol. Chem. 273: 29626-29634 (1998) and Petraush et al., J.Neurosci. 20: 8031-8041, J. Neurosci. 17: 5560-5572 (2000). In vitro andin vivo, inosine has previously been shown to induce neurons to expressa set of growth-associated proteins and to extend axons with the resultof axonal reorganization or “rewiring” of the brain. In adult rats withunilateral cortical infarcts, inosine stimulated neurons on theundamaged side of the brain to extend new projections to denervatedareas of the midbrain and spinal cord. This growth was paralleled byimproved performance on several behavioral measures. Chen et al., PNAS,99(13): 9031-9036 (2000). Inosine promotes axonal outgrowth of damagedneurons regenerating nerve connections.

[0088] Current therapies, both approved or in development, work byminimizing the damage to the affected territory of the brain, either byreversing the blockage (by clot dissolution) or protecting brain cellsfrom the ischemic injury (cytoprotective agents). However, once thedamage is complete, there is little to no functional recovery, sincethere is little to no nerve regeneration in the CNS that couldcompensate for the irreversible loss of the nerve cells and theirconnections. Although the current experimental results show inosine as avery promising treatment for stroke and TBI, in these studies inosinewas continuously administered (via a catheter into the ventricles) foran extended time period (from 24 hours to 28 days) using an Alzetosmotic pump.

[0089] Based on experimental results in animals, inosine effectively ispreferably administered directly into the CSF, which bathes the brain.In this way, the specifically injured brain tissue is exposed totherapeutic amounts of inosine while minimizing the potential forsystemic toxicity to be effective. It has been shown that inosinedelivered by intravenous administration shows little or no significantrecovery from limb function using the same animal model.

[0090] In order for inosine to become a universally commercial viabletreatment for stroke, inosine needs to be administered directly into theCSF over an extended time period. The polymer compositions describedherein, permit such extended delivery without substantial adverse sideeffects. The polymer compositions of the invention mediates delivery ofinosine to reach injured brain tissue in adequate concentrations toconfer clinical benefit to subjects suffering from a stroke. As usedherein, “clinical benefit” is defined by evaluating improved cognitionor motor function in an individual.

[0091] Citicholine

[0092] Citicholine (CDP-Choline or Cytidine-5′-diphosphocholine) is asmall, endogenous, naturally occurring substance found in mostlife-forms. It is an intermediate metabolite in the major pathwayphosphatidylcholine. Phosphatidylcholine is a phospholipid that is amajor component of cell membranes. Phosphatidylcholine is necessary forthe structure and function of all cells and is crucial for sustaininglife. Citicholine supplies choline to the brain to form acetylcholine.

[0093] Citicholine is a water-soluble molecule that does appear to beefficacious in treating both acute and chronic neurological disordersincluding, but not limited to, TBI, stroke, head trauma, Parkinsons andAlzheimers. See Secades and Frontera Meth. Find. Exp. Clin. Pharmacol.17: 2-54 and Weiss Life Sciences, 56(9): 637-660 (1995). See Adibhaltaet al., J. Neurochemistry, 80: 12-23 (2002). Both clinical andexperimental evidence has demonstrated efficacy to some moderate degreein TBI when given through the blood stream. However, citicholine rapidlyhydrolyzes once in the blood stream. This fact, combined with it's polarnature, making it less likely to diffuse across the BBB freely, resultsin less than 1 percent of any initial dose found in the brain. Thismakes citicholine an ideal candidate for a polymeric carriercomposition.

[0094] Citicholine has improved patient outcomes treating stroke inseveral clinical trails, but has shown no improvement in others. Themechanisms of action are thought to be (1) preventing fatty acidaccumulation; (2) promoting recovery of brain function by providing twocomponents, cytidine and choline, required in the formation of nervecell membrane; (3) promoting the synthesis of acetylcholine, aneurotransmitter associated with cognitive function.

[0095] Although the current experimental results show citicholine as avery promising treatment for stroke and TBI, experiments have shown thatmaximum neuroprotection is obtained when citicholine is continuouslyadministered over six days. See Hatcher et al., Soc. Neurosci. Abstract,25: 583 (1999) and Roa et al., J. Neurosci. Res., 58: 697-705 (1999). Tomake citicholine a universally commercial viable treatment for TBI andstroke, it appears citicholine needs to be administered directly intothe CSF over an extended time period.

[0096] When administered orally about 0.5% of the citicholine dosesuccessfully penetrate into brain tissue. See Agut et al.,Arzneim.-Forsch, 33: 1045-1047 (1983). When administered i.v., about 2%of the citicholine dose is successfully taken up into brain tissue. SeeFresta et al., Pharm. Res., 12: 1769-1774 (1995). Liposomes weresuccessfully used to increase the amount of citicholine to cross the BBBthus penetrate into brain tissue. By encapsulating citicholine withliposomes, the level citicholine reaching the brain was increased to˜23%. These results suggest that directly administering PLGA/citicholinepolymeric drug delivery compositions into the CSF will greatly increasethe levels of citicholine available to treat damaged brain tissue, thusgreatly improving clinical outcome of citicholine treatment.

[0097] Superoxide Dismutase (SOD)

[0098] Reactive oxygen species, such as superoxide radicals, are thoughtto underlie the pathogenesis of various diseases. Almost 3 to 10% of theoxygen utilized by tissues is converted to its reactive intermediates,which impair the functioning of cells and tissues. Superoxide dismutase(SOD) catalyzes the conversion of single electron reduced species ofmolecular oxygen to hydrogen peroxide and oxygen. There are severalclasses of SOD that differ in their metal binding ability, distributionin different cell compartments, and sensitivity to various reagents. Theenzyme from bovine and human erythrocytes contains copper and zinc, theone from chicken and rat liver mitochondria contains manganese while theenzyme from E. coli contains iron. Among these, Cu—Zn superoxidedismutase (SOD1) (Orgotein) is widely distributed and comprises 90% ofthe total SOD. This ubiquitous enzyme, which requires Cu and Zn for itsactivity, has great physiological significance and therapeuticpotential. SOD has been found to play a role in numerous central nervoussystem disorders including, but not limited to, stroke, TBI, familialamyotrophic lateral sclerosis (FALS), Parkinson's disease, Alzheimer'sdisease, dengue fever, cancer, multiple sclerosis, and Down's syndrome.See Noor et al., Med Sci Monit. 8(9):RA210-5 (2002).

[0099] Except for inosine, all current therapies (both approved or indevelopment) are focused on minimizing the damage to the affectedterritory of the brain, either by reversing the blockage (by clotdissolution) or protecting brain cells from the ischemic injury(cytoprotective agents). However, once the damage is complete, there islittle to no functional recovery, since there is little to no nerveregeneration in the CNS that could compensate for the irreversible lossof the nerve cells and their connections. Until now, the inability toprovide regeneration therapy for stroke and TBI has been due to theabsence of any effective compounds having the necessary in vivoregenerative activity.

[0100] In a preferred embodiment of the invention, inosine andciticholine are attached to a polymer composition (in the same orseparate particles) for the treatment of a stroke. Optionally, diseaseor traumatic injury is treated with a mixture of particles containing atleast one, preferably two, three, or more therapeutic agents to thecentral nervous system.

[0101] Size of Polymeric Particles of the Invention:

[0102] In a preferred embodiment, the polymeric particles of theinvention are spheres, although other forms of particles are includedwithin the scope of the invention as described above. To maximizeuniversal delivery, manufacturing spheres to the appropriate size torelease their load in a controlled manor is advantageous. To illustrate,smaller sphere's release more quickly than larger ones allowing for asustained release profile when a dose of various sizes is delivered.Ranges of size can be controlled with a sonication time and speed aswell as other mixing techniques. Sizes range infinitely and can beselected from a batch through common techniques such as filtration.Polymeric carriers which can flow freely in the CSF are about 25 μm dueto anatomical size limitations. Polymeric microspheres used in thisinvention as the carrier have a diameter of less than 100 μm, preferablyhaving a size ranging from about 0.1 to about 100 μm in diameter. Eventhough the microsphere can be of any size, the preferred size is 1-100μm, more preferably 2-75 μm, more preferably 3-50 μm, and even morepreferably about 5-25 μm.

[0103] Preferred sizes for nanospheres range from about 1 nanometer (nm)to about 100,000 nm in diameter. Optimally preferred diameters arewithin about 10 and 1,000 nm, preferably within 100 and 800 nm, and morepreferably within 200 and 500 nm.

[0104] Buoyancy of Particles:

[0105] The proper buoyancy—positive, neutral, or negative—of spheresensures that the spheres minimize and control the likelihood ofcollision and/or aggregation. When spheres flow more freely than overlynegatively buoyant spheres, collision is minimized, and collision and/oraggregation can interfere with their degradation. When spheres collideand/or aggregate, the result is a net decrease of surface area,resulting in increased variability of the release rate.

[0106] Buoyancy is adjusted to target the spheres and their agent(s) toor away from the brain or the spinal cord (the top or the bottom of theCNS). Buoyancy of the particles is engineered with negative buoyancysuch that the spheres aggregate in the sacral spine followingadministration. Such particles are useful for delivery of painmedications for a ruptured disk for treatment of sacral spinal cordinjury. Likewise, positively buoyant particles aggregate around thebrain to support therapeutic agents that have specificity (particularlycancer antagonists/blockers that bind to agonists/tags/trigers)characteristics making them more efficacious or citicholine fortreatment of stroke where it is advantageous to have speedy delivery.Buoyancy can range infinitely and are altered with the addition orelimination of buoyancy agents such as air, inert gas, oil, and/or othersubstances that are lighter than water or cerebral spinal fluid and canbe adjusted by adjusting the hardening time.

[0107] With a 95% confidence limit, the specific gravity (SG) of normalhuman CSF at 37° C. ranges from 1.0063 to 1.0075. See Levin et al.,Anesth Analg. 60(11):814-7 (1981). Those skilled in the art willrecognize that the SG of human CSF will vary to a small extentindividually.

[0108] To move particles towards and concentrate at the brain and upperregions of the central nervous system, particles are made positivelybuoyant, have a specific gravity less than 1.0063. Particles are madepositively buoyant by adding one or more of the following excipients tothe polymer matrix:

[0109] Non-Volatile Oils

[0110] Mineral Oil, Isopropyl Myrisate, Librafil™ 1944, Vegetable Oil,Glycerl Monostearate, Parrafin, Oelic Acid, Methyl Oelate, Lanolin,Petrolatin, Cetyl Alcohol, fish oil, Corn Oil, Soybean Oil, Vitamin E,polyalkyleneglycol such as polyethyleneglycol of various molecularweights, and Castor Oil.

[0111] Gases

[0112] Air, Nitrogen, Argon, Hydroflourocarbons, Carbon Dioxide, Helium,and Xenon.

[0113] To have particles remain neutrally buoyant and have the abilityto be carried throughout the CNS by the natural flow of the CSF,particles must have a specific gravity between 1.0063 and 1.0075.Particles are made neutrally buoyant by adding one or more of thefollowing excipients to the polymer matrix; Polysorbates, SorbitanEsters, and Polyoxyethylene Alkyl Ethyls.

[0114] To move particles towards and concentrate at the spinal cord andlower regions of the central nervous system, particles are madenegatively buoyant, have a specific gravity greater than 1.0075.Particles are made negatively buoyant by adding one or more of thefollowing excipients to the polymer matrix; Glycerin, AliphaticPolyesters, Gelatin, and Mannitol.

[0115] Methods to make microspheres positively buoyant in thegastrointestinal tract are described in Lee et al., J.Microencapsulation, 2001, 18:1, 65-75; Crotts et al., J. ControlledRelease”, 1995, 35, 95-105; Kawashima et al., J. Controlled Release,1991, 16, 279-290; and Lee et al., J. Microencapsulation, 16, 715-729.

[0116] Also within the scope of the invention is the use of sonicenergy, microwave energy, magnetic energy, or light energy, to help movethe compositions of the invention to specific tissues.

[0117] Manufacturing of Particles:

[0118] Spheres are prepared using standard methods, e.g., thosedescribed by Sandler, S. R.; Karo, W. Polymer Syntheses; Harcourt Brace:Boston, 1994; Shalaby, W.; Ikada, Y.; Langer, R.; Williams, J. Polymersof Biological and Biomedical Significance (ACS Symposium Series 540;American Chemical Society: Washington, D.C., 1994); and H. -P. Hentze,H. P. & Antonietti, M. Porus Polymers and Resins for Biotechnologicaland Biomedical Applications—Review in Molecular Biotechnology, 2002.Polymers are designed to be flexible; the distance between the bioactivesidechains and the length of a linker between the polymer backbone andthe group can be controlled. Other suitable polymers and methods fortheir preparation are described in U.S. Pat. Nos. 5,455,044 and5,576,018. Those skilled in the art will recognize that the polymericcarriers can be formed into various shapes, as described above.

[0119] The invention will be further described in the followingexamples, which do not limit the scope of the invention described in theclaims.

EXAMPLES Example 1 Preparation of Polymer Compositions—Microspheres

[0120] Various methods for preparing the polymeric particles of thepresent invention will be readily apparent to those skilled in the art,once armed with the present disclosure. Preferred methods for preparingthe carriers are discussed below in connection with the preferred PLGApolymeric delivery systems.

[0121] Specifically, in a preferred embodiment, a method formanufacturing polymer microspheres comprising at least one therapeuticagent and at least one buoyancy agent comprises the steps of: millingand/or sieving the therapeutic agent to the desired size range (about 5μm or less), dissolving the polymer solution in methylene chloride, oranother suitable solvent, (to make a 10% polymer/solvent solution),dispersing the therapeutic agent (e.g., Inosine) in polymer solution bystirring and/or shaking, stirring the agent/polymer solution whileadding silicone oil to create an emulsion, slowly (drop wise) adding theemulsion to hexane containing 0.5% w/w Span 85 that is being stirredrapidly and being sonicated by a sonic dismembrator, adding theappropriate amount of buoyancy agent, by mixing and/or agitating in away to achieve desired buoyancy, briefly sonciating and stirring for 20minutes. The spheres are then left to settle for about 5 minutes afterwhich the excess hexane is sucked off. Then 0.5% Span 85-hexane solutionis added bringing the total volume to 500 ml. The microspheres arere-suspended, briefly sonicated and stirred for 20 minutes. This processof settling and adding is repeated a few times until the desired rangeof sizes of microspheres is achieved. The microspheres are then vacuumdried overnight.

[0122]FIG. 2 shows a general process flow diagram of the preliminaryprocess. By modifying the critical process parameters of the preliminaryprocess, microspheres of three different sizes (about 1 μm, about 10 μm,about 25 μm) were made. The size of microspheres are modified by thefollowing parameters: shear force applied to emulsifydrug/polymer/solvent in emulsifying non-solvent; ratio ofdrug/polymer/solvent to hardening non-solvent and substitution ofsolvent and non-solvent chemicals.

[0123] The release profile of drug from PLGA/drug PCs can be manipulatedby the following process parameters: ratio of drug to PLGA (“DrugLoading”); molecular weight of PLGA and ratio of Lactide to Glycolide inPLGA.

[0124] The size of microspheres is determined using microscopytechniques. High performance liquid chromatography (HPLC) is used toquantify and determine release profiles. 5 ml of 10 mM PBS was added toPLGA/Inosine microspheres, that were manufactured using either ethylacetate or methylene chloride as the solvent. After about 3 hours, 4 mLof PBS was drawn off the sample and replaced with 4 mL of fresh PBS.This procedure was repeated at the end of each time interval. Inosineconcentration for the 4 mL aliquot of PBS was determined by HPLCanalysis. The cumulative amounts of inosine released over 10 days andrelease profiles are found in FIG. 10. Results indicate that formicrospheres manufactured using ethyl Acetate, 23.8% of the totalinosine was released over 10 days. Microspheres manufactured usingmethylene Chloride had about 44.2% of total inosine released over the 10day period.

[0125] Final determination of optimal size and release profiles, alongwith optimal route of administration is made by testing and evaluatingthe distribution of drug and PC distribution in-vivo.

[0126] In one example, PLGA/Inosine PCs were developed. Appropriatesteps are taken to ensure full solubility of Inosine to avoidcrystallization which can result in release profile variability. FIG. 3shows an image of PLGA/Inosine PCs.

Example 2 Investigating the Anatomical Distribution of Drug andFlourescein Loaded PCs

[0127] This experiment utilizes rats, allowing for PCs to circulate inthe cerebrospinal fluid (CSF). The animals are studied in 6 groups of 3.One half of the animals, 3 groups, are administered flourescein and aresacrificed for imaging after 48 hours to study distribution of spheresin CSF, spinal cord, and brain. The other half of the animals, 3 groups,are administered with drug-loaded PCs and are sacrificed for imagingafter one week to determine the concentration of drug in the CSF, spinalcord, and brain. The amount of fluorescein loaded into the PCs isdetermined by testing different amounts of flourescein for microspherefluorescence and encapsulation efficiency.

[0128] Animals are fasted from solid food for twelve hours prior to thestudy. Animals are pre-medicated with 6 mg/kg Xylazine, sq., and areanesthetized with a mixture of Xylazine, 10 mg/ml, and Ketamine, 40mg/ml, iv to effect. They are then intubated and transitioned toinhalation anesthesia, 1-2% Halothane in 02/N2O, 2/1, for the durationof the study.

[0129] Various routes of administration are tested. Among these variousroutes are intraventricular administration. Under sterile conditions,the scalp is opened in the midline and the skin and underlying musclereflected laterally to expose the skull. Under stereotactic guidance aneurosurgical burr is used to remove a small amount of skull bone andexpose the dura. Then, under stereotactic control, a catheter isintroduced into the area of interest, the lateral ventricle, bothventricles, and/or the subarachnoid space(s). Drug is then infused invarious doses into the areas of interest. Animals to be recovered willhave the hole in the skull packed with sterile Gelfoam, the muscles ofthe scalp closed in layers, and the skin closed with a runningsubcuticular suture.

[0130] In Cisterna Magna Administration (cisternal puncture), a sterilesyringe with a 48 gauge needle is loaded with a PC formulation. Fur isclosely shaved. Skin is cleansed and painted with iodine. The sterileneedle is inserted between the cervical vertebra, through dura materinto the cisterna at the base of the brain. The designated volume of PCformulation is then infused.

[0131] In the method of Intraspinal Administration (lumbar puncture), asterile syringe with a 48 gauge needle is loaded with a PC formulation.Fur is closely shaved. Skin is cleansed and painted with iodine. Thesterile puncture needle is passed directly in the midline, to andthrough the dura. The designated volume of PC formulation is theninfused.

[0132] Fluorescien particle Distribution is carried out as follows.After 48 hours, the animals that have been administeredfluorescienparticles are sacrificed under general anesthesia. The brainand spinal cord are carefully removed, fixed in 10% buffered formalin,and sectioned into slices. The slices are then placed on the microscopeand imaged using fluorescence filters to indicate the distribution ofspheres in CSF, spinal cord, and brain.

[0133] Drug Distribution is evaluated as follows. After seven days, theanimals administered drug particles are sacrificed under generalanesthesia. The CSF is then sampled, and the brain and spinal cord arecarefully removed. Concentration of drug in tissue and CSF is quantifiedusing high performance liquid chromatography. Spectra graphs ofindividual analytical samples is archived to record results.

Example 3 Intrathecal Administration of PLGA/Drug PCs in an EstablishedStroke Animal Model

[0134] Intrathecal administration of PLGA/Drug particles is compared toboth a bolus injection of drug and intraventricular pump delivery ofdrug in a rat middle cerebral artery occlusion (MCAo) stroke model. Thedrug is administered by three methods:

[0135] 1) Pump: Drug is administered into the ventricle using an Alzaosmotic pump (#2001 D) at a flow rate of 8 ul/hr over 24 hours.

[0136] 2) Lumbar Puncture: A bolus of drug is injected into the CSF viathe lumber region of the spine.

[0137] 3) Drug/PLGA PCs: Drug/PLGA particles are administrated by one ofthe methods described in Example 2.

[0138] Rats are used, because they are the smallest animal availablewith a spinal canal large enough to allow particles to circulate in theCSF. The animals will be studied in 3 groups of 12, plus control.

[0139] Rats are anesthetized with an intramuscular 4ml/kg “cocktail” ofKetamine (25 mg/ml), Xylazine (1.3 mg/mL) and Acepromazine (0.33 mg/mL).The common carotid arteries are exposed through a ventral midlinecervical incision in the neck. The temporalis muscle is bisected andreflected through an incision performed midway between the eye and theear drum canal. A 3 mm burr hole is made at the junction of thezygomatic arch and the squamos bone such that the bifurcation of thefrontal and parietal branch of the middle cerebral artery is exposed.The left middle cerebral artery is permanently occluded using a 10-0nylon suture directly below the bifurcation of the frontal and parietalbranch. Immediately after the MCAo, the common carotid arteries aretemporarily occluded using atraumatic aneurysm clips for one hour. Bodytemperature is maintained at 38° C.±1 throughout the entire procedure.Animals are sacrificed twenty-four hours from the time of MCA occlusionand the brains are removed for histological analysis.

[0140] Morphometric analysis is performed twenty-four hours after theinduction of focal ischemia. Rats are deeply anesthetized with CO₂ anddecapitated. The brain is removed and placed in ice chilled (˜4° C.)saline for fifteen minutes. Seven 2.0 mm coronal slices are cut using abrain cutting matrix and incubated in two percent 2,3,5triphenyltetrazolium chloride (TTC) for 20 minutes at 37° C. Slices areremoved, washed in saline and put into 10% formalin for 24 hours beforetissue analysis.

[0141] TTC is an established marker for functional mitochondrial enzymesand produces a visible deep red color within normal tissue. Ischemictissue, lacking mitochondrial activity, remains unstained and appearswhite. This is a standard method for use in image analysis of the slicedbrain and quantification of the ischemic area after MCAo.

[0142] Using the Image Pro-Plus imaging system, a total of 14 images perbrain of both the frontal and posterior side of each slice are analyzedthrough digital analysis. Digitizing and computation is done underblinded conditions. The total infarct volume is calculated for the lefthemisphere using the equation below.${{Volume}\quad \left( {mm}^{3} \right)} = {\frac{\Sigma \quad {area}\quad \left( {mm}^{2} \right)\quad {per}\quad {side}}{{{No}.\quad {of}}\quad {sides}\quad {analyzed}} \times 14\quad {mm}}$

[0143] The total infarct volumes are calculated for each animal andsubsequent group means are determined as volume of area (mm³). Data isnormalized to individual studies on a day to day basis because of thevariation in the cerebral vasculature in different rats and operatingroom conditions of that day. This results in less variability withineach study. Statistical analysis is performed using a two-tailed t-testand Dunnett's multiple comparison's.

Example 4 Process to Scale-Up Production of PLGA/Drug Particles for 3Months of Stability

[0144] Production of drug-loaded polymers is carried out as follows.

[0145] The microencapsulation process used is reproducible with thecapability of being scaled-up to support clinical trials. This processutilizes solvents and non-solvents that are safe.

[0146] After microencapsulation, particles of desired size are isolatedfrom the non-solvent using techniques such as centrifugation andtangential filtration.

[0147] Formulations are stable for at least three months under standardcondition. Size of microspheres are determined by microscopy.Photographs are taken to record results. High performance liquidchromatography is used to determine release profiles. Microspheres weremanufactured according to Example 1 using either ethyl acetate ormethylene chloride as the solvent. 5 mL of 10 mM PBS buffer was added tothe microspheres. After 3 hours, 4 mL of PBS was drawn off the sampleand replaced with 4 mL of fresh PBS. This procedure was repeated at theend of each time interval. Inosine concentration for the 4 mL aliquot ofPBS was determined by HPLC analysis. The cumulative amounts of inosinereleased over 10 days was determined, see FIG. 10. Microspheresmanufactured using ethyl acetate had about 23.8% of the total loadedinosine released after 10 days. Microspheres manufactured usingmethylene chloride had about 44.2% of the total loaded inosine releasedafter 10 days.

[0148] Final determination of optimal size and adequate releaseprofiles, along with optimal route of administration (as determined fromExample 2), are made by testing and evaluating the distribution of Drugand PC distribution in vivo (Example 3).

Example 5 Delivery of Neuroprotectant Agents into the CSF in a RatMiddle Cerebral Artery Occlusion (MCAo) Stroke Model

[0149] The parietal branch of the middle cerebral artery of theSprague-Dawley rat is permanently occluded with a 10-0 nylon suture. Thecommon carotid arteries are occluded temporarily for one hour. All drugsand vehicle are given beginning two hours post ischemia. Rats aresacrificed 24-hours later and the size of the infarct measured as apercent infarction of the total volume of the brain (mm³) using imaginganalysis. Prior to MCAo, drugs are administered into the ventricle usingan Alza osmotic pump (#20010) at a flow rate of 8 ul/hr over 24 hours. Afew drugs demonstrated efficacy in this model when delivered directly tothe CSF (FIG. 4).

[0150]FIG. 4 shows the infarct volume (mean±S.E.M.) pooled fromdifferent studies each of which included control animals. Animals weretreated with vehicle (n=23), Antioxidant (n=8), Prodrug (n=7) or an NMDAantagonist (n=7). All three test agents (Antioxidant, Prodrug and NMDAantagonist) were significantly different than the vehicle treated group(P<0.01).

[0151] Further studies with Citicholine established a dose responseeffect when given within the CSF (FIG. 5).

[0152] Squares of regenerated cellulose, polymer, cut into 1 mm sectionsare incubated at 37° C. in the different concentrations of drugsolutions for approximately 24 hours before being placed on the ratcortex. A 1×1 cm section of bone over the parieto-temporal region of therat brain is removed. The underlying dura is reflected and thepre-soaked squares are placed over the prospective infarctedtemporal-parietal region of the rat cortex. The overlying skin issutured and animals are returned to their cages.

[0153] In the MCAo rat model, the largest cortical infarct is apparentat 18 hours to three days after MCAo. A small lesion appears at threehours post MCAo and progresses rapidly by six hours to a sub-maximalinfarct, which is not statistically different than the 24 hour timeperiod. Therefore the regenerated cellulose-containing drug is placed onthe rat cortex two hours post MCAo. The results are summarized in FIG.6.

[0154]FIG. 6 shows the effects of the various neuroprotectant agents oninfarct volume in a rat model of focal ischemia when delivered by theSupracortical perfusion method. Test compound in 0.9% saline or vehiclealone began two hours after MCAo. The figure shows infarct volume(mean±S.E.M.) pooled from different studies each of which includedcontrol animals. Animals were treated with vehicle (n=23), Super OxideDismutase (n=8), Citicholine (n=7) or Dextromethorphan (n=7). All threetest agents were significantly different than the treated group(P<0.01).

Example 6 Inosine Stimulates Rewiring of Brain Circuits After Stroke

[0155] In one model, one side of the corticospinal tract in rats issevered as it courses through the brainstem. Inosine is then infuseddirectly into the motor cortex of the brain, the site of origin forthose axons descending into the non-injured side of the corticospinaltract. After 14 days of treatment, newly grown axon branches are tracedby injecting a dye into the treated nerve cells in the cortex. Animalsare then sacrificed and the spinal cord examined for histology evidenceof new axon growth.

[0156] Almost all of the treated animals showed signs of extensivecollateral sprouting of axons from the uninjured to the injured side ofthe corticospinal tract reaching below the level of thehemi-transection. These new axonal branches then continued to descenddown the injured side of the corticospinal tract, effectively replacingsevered axons with new ones. These axons were found to enter the graymatter of the spinal cord in a normal fashion. The number of collateral(new) axons ranged up to 2,500 per treated animal, compared to 28-170axons seen in control animals. These data indicate that thecorticospinal tract was extensively reconstituted following injury. Thisdata was obtained using an animal model of spinal cord injury in humans.

[0157]FIG. 7 shows a section through the spinal cord (cervicalenlargement). Area enlarged in A-F is shown by red box. A-C:Double-labeled section from a control animal treated with saline afterstroke. D-F: Similarly stained sections from an animal treated withinosine after stroke. A: After stroke, animals not treated with inosineshow very few axons that project from the intact hemisphere to the sideof the spinal cord which lost its normal input after stroke. D: Inosinetreatment causes many axons (red) to cross over from the undamaged sideof the brain to the denervated side of the spinal cord (arrows). B, E:The same sections, stained with antibodies to the growth-associatedprotein GAP-43, show very few newly growing axons on the denervated sideof the brain, but many in animals treated with inosine. C, F: Mergedimages showing coincidence of BDA- and GAP-43 labeled fibers (yellowstaining: arrows). The midline and medial-most fibers of the intact CSTare on the far right side of each frame. Scale bar 100 μm. See P. Chenet al., PNAS, 99(13): 9031-9036, 2002.

Example 7 A TBI Injury Model Utilizing the Dragonfly Lateral FluidPercussion Device

[0158] The development of a TBI injury model utilizing the Dragonflylateral fluid percussion device to create moderate to severe traumaticbrain injury in rats, is necessary to standardize the procedure andestablish a baseline for untreated injury to the brain parenchyma.Traumatic injury to the rat brain is performed using a modification ofthe lateral fluid percussion method first described by Macintosh et al.(Benowitz, L. I. et al., J. Biol. Chem. 273: 29626-29634, 1998;Petrausch, B. et al. J. Neurosci. 20: 8031-8041, 2000; J. Neurosci. 17:5560-5572; P. Chen et al., Inosine induces axonal rewiring and improvesbehavioral outcome after stroke, PNAS, 99(13): 9031-9036, 2002).

[0159] Male Sprague-Dawley rats (300-350 g) are anesthetized with eitheran intramuscular injection of Chloral Hydrate 4 mg/kg or a ketamine,xylazine and acepromazine cocktail. The head is shaved then prepped andmounted in a stereotaxic frame. Body temperature is maintained at37±0.5° C. during the procedure using a heating blanket connected to atemperature controller. A midline incision centered over the leftparietal cortex is performed. When the skull dries, suture lines appear.A 2 mm-diameter craniotomy is made at the level of the right parietalcortex (3.5 mm anterior to, 6 mm above the interaural line); the dura isleft intact at this opening. A 2.0 mm hollow female Leur-Loc placed overthe dura is fitted to the craniectomy site and anchored to the skullusing dental cement.

[0160] The Dragonfly Fluid Percussion Device (model # HPD-1700) isattached via a male Leur-Loc to the female Leur-Loc, implanted over theexposed dura of the rat. The device produces a saline pulse of increasedintracranial pressure (ICP) of varying volumes into the cranial cavity.Brief displacement and deformation of neural tissue results from therapid epidural injection of saline. Femoral artery cannulation isperformed and blood pressure is recorded throughout the procedure.

[0161] There are three levels of severity that can be produced:

[0162] Low-grade: 0-1.0 atm

[0163] Moderate: 1.5-2.0 atm

[0164] High-grade: 2.4-3.0 atm

[0165] Animals injured at pressures greater than 3.0-3.6 atm will sufferimmediate apnea and fail to recover unless assisted by a ventilatorPerri et al (Petrausch, B. et al. J. Neurosci. 20: 8031-8041, 2000; J.Neurosci. 17: 5560-5572, 2000). The applied cortical pressure pulse ismeasured extracranially by a electronic transducer coupled to anoscilloscope housed in the injury device.

[0166] Following FP brain injury, the Luer Loc is removed, the incisionis sutured with 4-0 silk, a layer of triple antibiotic ointment isapplied to the closure, and the animals are returned to their cages.

[0167] Morphometric analysis is performed to quantify infarction.Twenty-four hours after the induction of focal ischemia, rats are deeplyanesthetized with CO₂ and decapitated. The brain is removed and placedin ice chilled (˜4° C.) saline for fifteen minutes. Seven 2.0 mm coronalslices are cut using a brain cutting matrix and incubated in two percent2,3,5 triphenyltetrazolium chloride (TTC) for 20 minutes at 37° C.Slices are removed, washed in saline and put into 10% formalin for 24hours before tissue analysis.

[0168] TTC is an established marker for functional mitochondrial enzymesand produces a visible deep red color within normal tissue. Injuredtissue, lacking mitochondrial activity, remains unstained and appearswhite. This is a standard method for use in image analysis of the slicedbrain and quantification of the ischemic area after MCAo. Using theImage Pro-Plus imaging system, a total of 14 images per brain of boththe frontal and posterior side of each slice are analyzed throughdigital analysis. Digitizing and computation is done under blindedconditions. The total injury volumes are calculated for each animal andsubsequent group means are determined as volume of area (mm³). The totalinjury volume is calculated for the left hemisphere using the equationbelow.${{Volume}\quad \left( {mm}^{3} \right)} = {\frac{\Sigma \quad {area}\quad \left( {mm}^{2} \right)\quad {per}\quad {side}}{{{No}.\quad {of}}\quad {sides}\quad {analyzed}} \times 14\quad {mm}}$

Example 8 In Vitro Study of Controllably Buoyant Polymeric Particles

[0169] Polymeric carriers containing buoyancy agents are manufactured asdiscussed in Example 1. To move particles towards and concentrate at thebrain and upper regions of the central nervous system, the polymericparticles are manufactured to have a specific gravity less than 1.0063.Particles are made positively buoyant by adding one or more of thefollowing excipients to the polymer matrix: Mineral Oil, IsopropylMyrisate, Librafil™ 1944, Vegetable Oil, Glycerl Monostearate, Parrafin,Oelic Acid, Methyl Oelate, Lanolin, Petrolatin, Cetyl Alcohol, Corn Oil,Soybean Oil, and Castor Oil, Air, Nitrogen, Argon, Hydroflourocarbons,Carbon Dioxide, Helium, and Xenon.

[0170] To have particles remain neutrally buoyant and have the abilityto be carried throughout the CNS by the natural flow of the CSF,particles are manufactured that have a specific gravity between 1.0063and 1.0075. Particles are made neutrally buoyant by adding one or moreof the following excipients to the polymer matrix; a Polysorbate, aSorbitan Ester, and a Polyoxyethylene Alkyl Ethyl.

[0171] To move particles towards and concentrate at the spinal cord andlower regions of the central nervous system, particles are manufacturedto have a specific gravity greater than 1.0075. Particles are madenegatively buoyant by adding one or more of the following excipients tothe polymer matrix; Glycerin, Aliphatic Polyesters, Gelatin, andMannitol.

[0172] Positively buoyant, neutrally buoyant and negatively buoyantpolymeric carriers (in this example, microspheres) are separatelysuspended in a device designed to simulate a patient assuming an uprightposition. A device with the ability to control flow rates is used tohouse cerebrospinal fluid. The device has a temperature control thatmaintains the fluid at 37° C. A pulse may be added to simulate thechoroidal pulse from vascular flow. A manometer is included to measurepressures on the proximal side of the valve, to maintain them at normalrange. Microspheres are added to the device. Positively buoyantmicrospheres are seen floating at the top of the device, while neutrallybuoyant microspheres are floating at approximately the same location asoriginally placed. Negatively buoyant microspheres fall towards thebottom of the device. These studies indicate that microspheres aremanufactured to move within the CNS and target specific areas of diseasestate.

[0173] Buoyancy is also evaluated as follows. Positively buoyant,neutrally buoyant and negatively buoyant polymeric carriers (in thisexample, microspheres) are individually suspended in a graduatedcylinder containing either sterile saline water or cerebral spinal fluidand brought to 37° C. using a temperature controlled water bath. Themicrospheres are allowed to flow freely within the graduated cylinder.Positively buoyant microspheres float at the top of the graduatedcylinder, while neutrally buoyant microspheres float at approximatelythe same location as originally located. Negatively buoyant microspheresfall towards the bottom of the graduated cylinder.

Example 9 In Vivo Studies with Fluorescein to Determine CompositionLocation

[0174] Polymer compositions are prepared as described in Example 1. Adetectable label, such as a fluorescent moiety, is added during themanufacturing process so that real-time detection of the microspheres ispossible. Microspheres that were found to be negatively buoyant,neutrally buoyant and positively buoyant are injected intrathecally to asubject that is maintained in an upright position. After a certainperiod of time, a diagnostic medical instrument is used to determine thelocation of the microspheres. In this way, it is possible to determinethe anatomical location of the polymer compositions.

What is claimed is:
 1. A biocompatible composition comprising atherapeutic agent, a polymer and a buoyancy agent.
 2. The composition ofclaim 1, wherein the polymer is biodegradable.
 3. The composition ofclaim 1, wherein the composition is controllably buoyant within thecerebrospinal fluid.
 4. The composition of claim 1, wherein saidbuoyancy agent has a specific gravity of between about 1.0063 to about1.0075.
 5. The composition of claim 1, wherein said buoyancy agent has aspecific gravity greater than about 1.0063
 6. The composition of claim1, wherein said buoyancy agent has a specific gravity less than about1.0063
 7. The composition of claim 1, wherein said therapeutic agent isa neuroprotective agent and said composition is administered to asubject having a central nervous system disorder.
 8. The composition ofclaim 1, wherein said buoyancy agent is a mixture of oxygen andnitrogen.
 9. The composition of claim 1, wherein said buoyancy agent isa hydrofluorocarbon.
 10. The composition of claim 1, wherein saidbuoyancy agent is a gas selected from the group consisting of nitrogen,argon, carbon dioxide, helium, and xenon.
 11. The composition of claim1, wherein said therapeutic agent is selected from the group consistingof inosine, citicholine, SOD, and dextrorphan.
 12. A compositioncomprising a first polymeric particle comprising a first therapeuticagent and a second polymeric particle comprising a second therapeuticagent, wherein said first and said second polymeric particles comprise abuoyancy agent.
 13. The composition of claim 12, wherein said ratio ofsaid first polymeric particle and said second polymeric particle is50:50.
 14. The composition of claim 12, wherein said ratio of said firstpolymeric particle and said second polymeric particle is 60:40.
 15. Thecomposition of claim 12, wherein said ratio of said first polymericparticle and said second polymeric particle is 40:60.
 16. Thecomposition of claim 2, wherein said biodegradable polymer is anaturally derived polymer selected from the group consisting of albumin,alginate, cellulose derivatives, collagen, fibrin, gelatin, andpolysaccharides.
 17. The composition of claim 2, wherein saidbiodegradable polymer is a synthetic polymer selected from the groupconsisting of polyesters, polyethylene glycol, poloxomers,polyanhydrides, and pluronics.
 18. The composition of claim 17, whereinsaid synthetic polymer is poly(lactide-co-glycolide).
 19. Thecomposition of claim 1, wherein said therapeutic agent is selected fromthe group consisting of L-dopa, dopamine, carbidopa, choline,acetylcholine, cholinergic neuronotropic agents, gangliosides, nervegrowth enhancing agents, living cells such as bone marrow cells or fetalneural tissue or stem cells, enzymes, antipsychotropic agents,antidepressants, excitatory amino acid antagonist or agonist,antiepileptic medications enzymes and combinations thereof as well asantioxidants, nonsteroidal anti-inflammatory drugs (NSAIDS), steroidalanti-inflammatory agents, calcium channel blockers, NMDA antagonists,inosine, citicholine, SOD, dextrorphan, aspirin, andtetramethylpyrazine.
 20. The composition of claim 1, wherein saidtherapeutic agent is a cancer agent selected from the group consistingof vinca alkaloids and other plant products, cytostatic drugs, cytotoxicdrugs, hormones (estrogens and anti-estrogens), alkylating agents,immunomodulators (immunostimulators and immunosuppressives),hematological agents, non-steroidal products, radiopharmaceuticals,antibodies, antiandrogens, and epidermals.
 21. The composition of claim7, wherein said central nervous system disorder is selected from thegroup consisting of cancer, Parkinson's disease, Alzheimer's dementia,Huntington's disease, epilepsy, ALS, MS, antibiotic delivery, trauma,stroke, TBI, depression, spinal cord injury, pain management and othertypes of neurological and psychiatric illnesses.
 22. A method foradministering a therapeutic agent within the central nervous system of asubject, the method comprising contacting a central nervous systemtissue with a biodegradable polymer composition comprising a therapeuticagent, a polymer and a buoyancy agent.
 23. The method of claim 22,wherein said subject is diagnosed with a central nervous systemdisorder.
 24. The method of claim 23, wherein said composition is in theform of a plurality of spherical particles from about 1 to about 25 μmin diameter.
 25. The method of claim 23, wherein the therapeutic agentis selected from the group consisting of L-dopa, dopamine, carbidopa,choline, acetyl choline, cholinergic neuronotropic agents, gangliosides,nerve growth enhancing agents, living cells such as bone marrow cells orfetal neural tissue or stem cells, enzymes, antipsychotropic agents,antidepressants, excitatory amino acid antagonist or agonist,antiepileptic medications enzymes and combinations thereof as well asantioxidants, nonsteroidal anti-inflammatory drugs (NSAIDS), steroidalanti-inflammatory agents, calcium channel blockers, NMDA antagonists,inosine, citicholine, SOD, dextrorphan, aspirin, andtetramethylpyrazine.
 26. The method of claim 23 wherein the therapeuticagent is a cancer agent selected from the group consisting of vincaalkaloids and other plant products, cytostatic drugs, cytotoxic drugs,hormones (estrogens and anti-estrogens), alkylating agents,immunomodulators (immunostimulators and immunosuppressives),hematological agents, non-steroidal products, radiopharmaceuticals,antibodies, antiandrogens, and epidermals.
 27. The method of claim 23,wherein the contacting a central nervous system tissue is by intrathecaladministration directly into the cerebrospinal fluid of the subject. 28.The method of claim 23, wherein the central nervous system disorder isselected from the group consisting of cancer, Parkinson's disease,Alzheimer's dementia, Huntington's disease, epilepsy, ALS, MS,antibiotic delivery, trauma, stroke, TBI, depression, spinal cordinjury, pain management and other types of neurological and psychiatricillnesses.
 29. The method of claim 23, wherein said biodegradablepolymer is a naturally derived polymer selected from the groupconsisting of albumin, alginate, cellulose derivatives, collagen,fibrin, gelatin, and polysaccharides.
 30. The method of claim 23,wherein said biodegradable polymer is a synthetic polymer selected fromthe group consisting of polyesters, polyethylene glycol, poloxomers,polyanhydrides, and pluronics.
 31. The method of claim 23, wherein saidsynthetic polymer is poly(lactide-co-glycolide).
 32. The composition ofclaim 12, wherein said first therapeutic agent is inosine and saidsecond therapeutic agent is citicholine.
 33. The composition of claim 1,wheren said buoyancy agent is selected from the group consisting of fishoil, vegetable oil, vitamin E oil, and PEG.